On 12/30/2011 12:45 PM, Al Kozakiewicz wrote:
> That's really interesting.
> Jim Lux already mentioned the pitfalls of GPS and barometric measurements of
> altitude. The technology of ILS doesn't require a functioning altimeter to
But flying IFR does. They are on the minimum equipment list.
> and I don't believe IFR rules allow landing without some minimum visibility
Class I allows for landing when you can't even see the runway AFTER
landing. This is an "auto land" system used by air carriers in the US.
Not all aircraft or airports are equipped for this type of landing. In
addition the *pilots* must be certified for this type of landing as well.
> - enough to render a functioning altimeter "optional" on approach. The
> point being that no one expects a barometric altimeter to be accurate enough
> to be the only reference for height above ground as you land.
It depends on the particular airport and class of aircraft. Your
approach plates or charts list the minimums for each approach.
You have two minimums. One is the ceiling the other is distance close to
the surface called Runway Visual Range, or RVR. For KMBS, a major
airport near me, the minimum ceiling is 200 feet on the ILS. Visibility
or RVR for small planes (based on stall speed) may be as low as a
quarter mile and it may be a 1/2 mile to a mile for much larger
aircraft. Landing with 200 and a quarter is only for those with
experience and who are proficient at doing it. I come across the
threshold at 120 MPH which is very close to where I reach decision
height which is 200 feet. With a quarter mile visibility and 200 foot
ceiling you can only see a spot of runway under you and virtually
nothing ahead. Only when getting near the surface may you be able to see
that quarter mile. Imagine driving your car down a highway at 120 MPH
and only being able to see a 1/4 mile.
> Many, if not most, USGS elevation benchmarks were set using a rod and level
> starting in the 19th century. They are surprisingly accurate considering
> that those in the middle of the country are more than a thousand miles from
> the nearest ocean.
> As an aside, I thought I had read that Google Earth had a problem with
> elevations. I don't remember the exact circumstances, but the context was
> some sort of modeling as GE assumes a spherical earth. Basically, GE
> underestimates altitudes and sea levels at low latitudes due to the "bulging"
> of the earth at the equator. That sound familiar to anyone?
> From: email@example.com [firstname.lastname@example.org] On
> Behalf Of Mike Ashby [email@example.com]
> Sent: Friday, December 30, 2011 11:49 AM
> To: firstname.lastname@example.org
> Subject: Re: [TowerTalk] FAA& Private Airstrips
> I just finished making application to the FAA and after about 60 days
> received back a "Notice of presumed HAZARD to air navigation" letter from
> them. This has since has been resolved and I now have received the go ahead
> to install a tower. QTH is 5572 feet south of a very small municipal
> airport. Tower location falls in the first ring around the airport marked by
> the FAA as "Horizontal Surface elevation: 150 feet". 10 feet further east on
> my 10 acre property begins the outer ring around the airport marked "Conical
> Surface 20:1"
> One would think that in the 1st ring the tower could be 150 ft in height and
> in the 2nd ring it could be 278 ft in height, (5572/20)...........I did.
> Started application by taking some quick elevation measurements with GPS unit
> and made application for a 120 foot tower, it was rejected. After long
> discussion with FAA, took a trip over to the airport to talk with the
> manager. I wanted to find the airport elevation marker for the airstrip.
> They didn't know where it was. The sign at the entrance to the property
> posted the elevation as 5680 ft. The FAA shows it as 5637 ft. I asked a
> pilot of a small commercial jet, that was sitting of the airstrip what his
> altimeter was reading and he said 5605 ft. (That would be 32 ft below the
> official FAA surface of the runway elevation). Went into town and found an
> official USGS survey marker and calibrated my GPS. Went back to QTH and
> remeasured, nothing was looking good for me. Called FAA, discussed my
> d I would use same thing that they were checking
> with...................GOOGLE EARTH! Plugged in all of the measurements,
> adjusted tower height down to 110ft, (could have gone as high as 113 ft but
> didn't want to press my luck), sent changes back to FAA and received approval
> next day. So much for the "150 ft zone" and the "20:1"
> zone.............never did get a good explanation as to why not, just happy
> to get what I got.
>> From: email@example.com
>> Date: Fri, 30 Dec 2011 10:50:10 -0500
>> To: firstname.lastname@example.org
>> CC: email@example.com
>> Subject: Re: [TowerTalk] FAA& Private Airstrips
>> Unless you have a deep hatred for airplanes and people who fly
>> them......please contact the owner/operator of the airstrip and inform them
>> of the position and hight of your tower.
>> 73 Ed KB3TOX
>> On 29 Dec, 2011, at 7:56 PM, William Hein wrote:
>>> My family and I recently moved to a wonderful house in beautiful Glade Park
>>> CO (on the other side of Colorado National Monument from Grand Junction.
>>> The house itself is an ultra-energy efficient Earthship (Google "Glade Park
>>> Earthship" for more info). We have 35 rural acres of land around our house
>>> in a low population density rural area. All in all it's going to be a
>>> great place for ham radio.
>>> The FAA Website TOWAIR indicated that "Structure does not require
>>> registration"after I plugged in my coordinates along with elevation
>>> (6840-ft ASL approx.). There are no airports within 8 kilometers (5 miles)
>>> of the coordinates you provided." TOWAIR went on to caution "TOWAIR's
>>> findings are not definitive or binding". Since "Pinyon Airport" (a rather
>>> pretentious designation for a grass airstrip with a windsock) is 5.5 km
>>> away I am guess it is either not registered with the FAA or somehow doesn't
>>> count as a real airport.
>>> I have a 142-foot Big Bertha tower which I previously had installed in
>>> Vermont which I intend to reinstall here along with at least one other
>>> 100-ft + tower and a few smaller structures. For many reasons I'd hate to
>>> see a airplane run into Bertha.
>>> So what should I do now? Contact the FAA for an opinion? Find out who
>>> owns the airstrip and give them a verbal or written heads up on my tower
>>> plans and also request they avoid flying low over my house? Something else?
>>> William Hein, AA7XT
>>> (ex-AA4XT, NT1Y, AA6TT, KC6EDP)
>>> TowerTalk mailing list
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